Rotational vessel heating

ABSTRACT

Aqueous fluids are heated or boiled in a tank or vessel by causing cavitation in the fluid within the tank or vessel. A rotor having cavities on its cylindrical surface is rotated within a closely dimensioned housing submerged in the fluid, deliberately causing cavitation which heats the aqueous fluid without the use of flame or heat exchange surface. An electric motor which powers the rotor may itself be submerged in the tank or boiler vessel. The rotor includes radial channels for imparting centrifugal impetus to the fluid as it flows toward the cavitation zone.

TECHNICAL FIELD

The invention is a liquid heater which heats a reservoir of aqueous liquid by inducing flux stress within the liquid. A flux stress inducing device, which may be a cavitration device, including its electric motor in one version, is immersed in the liquid in the vessel. Hot water, steam, vapor and blowdown are readily removed from the reservoir in a conventional manner.

BACKGROUND OF THE INVENTION

It is known that turbulence, shear, and cavitation within a liquid will elevate its temperature. For many purposes, the generation of shear, turbulence and cavitation is considered to be a waste of energy, and much attention in pump design, for example, has been devoted to avoiding or suppressing these effects. Some workers, however, have sought to take advantage of the fact that the temperature of the liquid may be elevated without the use of flame or even a heat transfer surface of any kind, and have designed machines deliberately to subject the fluid in them to such tortuous flow. Typically, the liquid passes through the machine for heating and flows to a different location for heat transfer or other use, and is continuously recycled to the machine. See, for example, Pope U.S. Pat. No. 5,341,768.

While the art has used such machines for heating flowing liquids, to our knowledge it has not successfully designed an apparatus to elevate the temperature of a body of water within a vessel, tank, boiler, or other reservoir by turbulence, shear, and/or cavitation

SUMMARY OF THE INVENTION

We have invented a water heater using a flux stress device to supply heat. The flux stress device is immersed within the water heater reservoir. Placing the flux stress device within the reservoir enables excellent circulation of hot liquid within the vessel (reservoir) and excellent control of the heating process. The flux stress device can heat a wide variety of solutions and slurries.

It is known to convert mechanical energy into thermal energy in a fluid by causing the fluid to follow a tortuous or stressful path to create shear, turbulence, cavitation or a combination of one or more of these. A tortuous path may be one featuring diversions, obstacles or protuberances which induce significant turbulence. An example of a stressful path for generating shear is one passing between two closely opposing surfaces, one of which is advantageously moving with respect to the other. A paradigm of a cavitation path is a path including cavities capable of alternately creating and imploding low-pressure vacuities in the fluid. We use the term “flux stress” to describe generically all three of these effects, and a flux stress device to mean any device which will elevate the temperature of a fluid by flux stress. It is immaterial for our purposes whether the flux stress causes an alteration or physical degradation of a component of the fluid, such as a viscosity-imparting polymer. We define “flux stress” as shearing (sometimes called “shear stress,” or simply “shear”), turbulence, or cavitation, or a combination of more than one of these, resulting in the heating of a fluid, wherein thermal energy is induced in the fluid by the stress of the shearing, turbulence, or cavitation. In addition, some devices of the prior art recognize friction within a device as an effect which will heat fluid in it. In many such prior art cases, friction implies primarily a form of stress caused by flowing against solid parts which may or may not be designed deliberately to cause a tortuous flow, and may even in some cases imply the generation of heat due to the motion or resistance of solid particles suspended in the fluid. Because turbulence-induced heat is the primary result in either case, we do not intend to exclude friction, so defined, as a phenomenon which elevates the temperature of the fluid in a flux stress device.

The substantially parallel surfaces frequently used to create shearing and/or turbulence need not be planar or cylindrical surfaces—for example, a conical surface may be nested within and close to another conical surface, and the fluid caused to flow between the two surfaces, one or both of which may be turning; if both are turning, they will advantageously turn in opposite directions. Turbulence and shearing between two closely aligned surfaces or within a conduit or passage induces thermal energy within the fluid from the mechanical energy of the fluid flux, without dependence on a heat transfer surface, and the generation of thermal energy may be enhanced by rotating or otherwise moving one surface with respect to the other while the fluid is caused to pass between them.

Cavitation devices are designed deliberately to generate heat by cavitation. Cavitation occurs in a fluid when the fluid flows in an environment conducive to the formation of partial-vacuum spaces or bubbles within the fluid. Since the spaces or bubbles are partial vacuum, they almost immediately implode, causing the mechanical or kinetic energy of the fluid to be converted into thermal energy. In many devices, such as most pumps, cavitation is an occurrence to be avoided for many reasons, not least because of convulsions and disruption to the normal flow in the pump, but also because of the loss of energy when the mechanical energy of the pump is converted to undesired heat instead of being used to propel the fluid on a desired path. There are, however, certain devices designed deliberately to achieve cavitation in order to increase the temperature of the fluid treated. Such cavitation devices are manufactured and sold by Hydro Dynamics, Inc., of Rome, Ga., most relevantly the devices described in U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and particularly 5,188,090, all of which are hereby specifically incorporated herein by reference in their entireties. These patents may be referred to below as the HDI patents.

The basic design of the cavitation devices described in the HDI patents comprises a cylindrical rotor having a plurality of cavities bored or otherwise placed on its cylindrical surface. The rotor turns within a closely proximate cylindrical housing, permitting a specified, relatively small, space or gap between the rotor and the housing. Fluid usually enters at the face or end of the rotor, flows toward the outer surface, and enters the space between the concentric cylindrical surfaces of the rotor and the housing. While the rotor is turning, the fluid continues to flow within its confined space toward the exit at the other side of the rotor, but it encounters the cavities as it goes. Flowing fluid tends to fill the cavities, but is immediately expelled from them by the centrifugal force of the spinning rotor. This creates a small volume of very low pressure within the cavities, again drawing the fluid into them, to implode or cavitate. This controlled, semi-violent action of micro cavitation brings about a desired conversion of kinetic and mechanical energy to thermal energy, elevating the temperature of the fluid without the use of a conventional heat transfer surface.

Benefits of the HDI cavitation devices include that they can handle slurries as well as many different types of solutions, they can be used to concentrate such slurries and solutions by facilitating the removal of steam and vapor from the fluid being treated, and the heating of the fluid occurs within the fluid itself rather than on a heat exchange surface which might be vulnerable to scale formation and ultimately to a significant reduction in heat transfer.

Definition: We use the term “cavitation device” to mean and include any device designed to impart thermal energy to flowing liquid by causing bubbles or pockets of partial vacuum to form within the liquid it processes, the bubbles or pockets of partial vacuum being quickly imploded and filled by the flowing liquid. The bubbles or pockets of partial vacuum have also been described as areas within the liquid which have reached the vapor pressure of the liquid. The turbulence and/or impact, sometimes called a shock wave, caused by the implosion imparts thermal energy to the liquid, which, in the case of water, may readily reach boiling temperatures. The bubbles or pockets of partial vacuum are typically created by flowing the liquid through narrow passages which present side depressions, cavities, pockets, apertures, or dead-end holes to the flowing liquid; hence the term “cavitation effect” is frequently applied, and devices known as “cavitation pumps” or “cavitation regenerators” are included in our definition. Steam generated in the cavitation device can be separated from the remaining, now concentrated, water and/or other liquid which frequently will include significant quantities of solids small enough to pass through the device. The term “cavitation device” includes not only all the devices described in the above itemized HDI U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and 5,188,090 but also any of the devices described by Sajewski in U.S. Pat. Nos. 5,183,513, 5,184,576, and 5,239,948, Wyszomirski in U.S. Pat. No. 3,198,191, Selivanov in U.S. Pat. No. 6,016,798, Thoma in U.S. Pat. Nos. 7,089,886, 6,976,486, 6,959,669, 6,910,448, and 6,823,820, Crosta et al in U.S. Pat. No. 6,595,759, Giebeler et al in U.S. Pat. Nos. 5,931,153 and 6,164,274, Huffman in U.S. Pat. No. 5,419,306, Archibald et al in U.S. Pat. No. 6,596,178 and other similar devices which employ or include a shearing effect between two close surfaces, at least one of which is moving, such as a rotor, and/or at least one of which has cavities of various designs in its surface (a cavitation zone) as explained above. Shearing and turbulence commonly occurs in cavitation devices, and possibly should not be ignored in considering their heat generating abilities, but most of the thermal energy imparted to the liquid in a cavitation device is by way of cavitation, by definition.

As a means for heating or boiling water or other aqueous fluids, the existing designs of cavitation devices exhibit many benefits, but there remains a need for improvement. It is difficult to control the separation of steam and vapor from the remaining concentrated liquid at the exit of the device. As one approach to this problem, at least a portion of the heated throughput of the cavitation device may be sent to a flash tank, for the separation of liquid and gaseous or vapor phases, thus necessitating a whole set of additional equipment, valves and controls. Also, the typical cavitation device would benefit from a practical method of maintaining pressure on the cavitation zone, to enhance the cavitating effect.

Our invention includes a boiler using a cavitation device to supply heat. The cavitation device is within the boiler vessel and may be totally immersed. Placing the cavitation device within the vessel enables excellent circulation of hot fluid within the vessel and recycling of the fluid through the (desirably) immersed cavitation device to provide excellent control of the heating process entirely within the vessel. The cavitation device can heat a wide variety of solutions and slurries.

While we describe our invention as in many instances using a cavitation device, we may also use various flux stress devices which do not provide heating by cavitation. Such devices include, broadly, dynamometers (some of which have come to acquire that name in spite of the fact they may not measure anything) and water brakes. Water brakes and other types of absorbing dynamometers convert the energy of a rotor on a turning shaft into thermal energy due to the turbulence and/or shear stress generated in the fluid passed by it in proximity to another surface, some of which may include protuberances to cause local turbulence but not cavitation.

Our invention includes a method of making steam comprising causing flux stress by a flux stress device at least partially submerged in a body of aqueous fluid within a reservoir, which may be called a boiler or boiler vessel.

Our invention includes a method of making steam comprising causing cavitation by a cavitation device at least partially submerged in a body of aqueous fluid within a boiler. By “aqueous fluid” we mean liquid water such as would normally occupy a significant portion of a boiler vessel. But because of the ability of our invention to handle a wide variety of solutions and slurries, we intend for the term “aqueous fluid” to include solutions and slurries of water including up to and even in excess of 50% non-water materials by weight, either dissolved, particulate (if the particulates are suspended in the liquid, they will desirably be of a size able to pass through the cavitation device), or both, and including the possibility of organic liquids and/or other non-aqueous liquids. For example, the term aqueous fluid thus includes many types of industrial fluids, including used oilfield fluids. The cavitation device will normally be immersed in the aqueous fluid, but can operate when it is only partially submerged. Our invention thus includes a boiler or boiler vessel having a cavitation device within the boiler or boiler vessel as a source of heat. Our invention is useful for heating or boiling any aqueous fluid as defined above.

Any such aqueous fluid is introduced to a reservoir and removed as heated fluid, either as a liquid, steam, or vapor. This process may be substantially continuous, as is frequently the case with a boiler, or it may be intermittent, as is commonly the case with a water heater. Our objective is to heat the body of water in the reservoir where it is utilized as a source or supply of steam, vapor, or heated liquid. To further describe this process, we use the term “makeup liquid” for the aqueous fluid which is continuously or intermittently introduced to the reservoir, which may be a boiler vessel. Makeup liquid is fresh incoming liquid in the sense that it is not recycled from the reservoir.

We use the word “reservoir” for its dictionary meaning, “a receptacle or chamber for storing a fluid.” We use it to include the term “vessel.” “Reservoir” is used in the context of our invention to emphasize that the flux stress device is immersed in aqueous fluid within the receptacle or chamber, sometimes herein called a vessel, capable of “storing” as that term is used in the definition of “reservoir.” That is, the reservoir serves as a more or less continuously available source of hot water, steam or vapor, which may be continuously or intermittently removed from it while the source is continuously or intermittently replenished by makeup liquid. While the aqueous fluid will pass through the cavitation device or other flux stress device, and therefore may circulate substantially continuously within the reservoir so that it will circulate through the flux stress device to attain higher temperatures, once the heated aqueous fluid is removed from the reservoir either as hot fluid or steam, it does not return, as it normally will be consumed or expended in any of many possible ways. The reservoir containing the flux stress device may be called either a water heater (aqueous fluid, or liquid, heater) or a boiler, depending on the temperatures and pressures achieved, and the purpose of the apparatus. However, the definition of “boiler” includes a vessel used to heat liquid broadly—that is, it applies to reservoirs, containers, and tanks wherein liquid is heated, whether or not the liquid actually boils and/or whether or not steam is generated. Further, the objective that the heated or gasified liquid will be consumed or expended either continuously or intermittently should not be read to mean that we rule out that some portion of the fluid may be recycled after the fluid has left the reservoir. And, we use the term “boiler vessel” to mean a vessel for holding a liquid which may be boiled, but need not be. Boiler vessels generally are constructed to provide for a specified liquid level or range of levels, and a free space above the liquid in which steam and vapor is contained, generally under pressure. For many purposes, it will be desirable for the boiler vessel to be a reservoir capable of handling pressures of up to 250 pounds per square inch, and desirably at least 500 pounds per square inch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section, in outline, of a boiler of our invention.

FIG. 2 shows a construction similar to FIG. 1, from a different perspective.

In FIG. 3, a variation is shown in which both the electric motor and the cavitation device are immersed in the boiler vessel; the rotor is mounted on a vertical axis.

In FIGS. 4 a, 4 b, 4 c, and 4 d, details of a cavitation device rotor useful in our invention are shown.

FIG. 5 is a sectional view of a particular design for the rotor of the cavitation device.

In FIG. 6, the boiler vessel wall is used for the cylindrical housing of the cavitation device.

FIG. 7 shows a modification designed to circulate the boiling fluid in a particular manner.

In FIG. 8, the use of a water brake heater within the reservoir is shown.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, vessel 1 is capable of containing a desired quantity of boiling water and steam as well as the equipment to be described. It has a blowdown outlet 2 and a dry steam outlet 3. Other conventional outlets and entrances, not shown, may be built into vessel 1—for placing equipment, for repairs, for removal of hot aqueous fluid other than blowdown, independently introducing aqueous fluid, and any other desired purpose. On the lower part of the left side of vessel 1, as depicted, is a cylindrical cavitation rotor 4 having cavities 5 formed on its cylindrical surface. The rotor 4 is designed to rotate within a hollow cylindrical housing 6 which may substantially surround the cylindrical surface of rotor 4. In this configuration, the circular face 7 of rotor 4 is not enclosed—that is, it is in direct contact with hot or boiling aqueous fluid 20. The rotor 4 is turned by engine or motor 9 mounted outside the vessel 1 and having a shaft 10 connected to the rotor. The connection may be through a set of gears or other mechanical power transmitting devices not shown. Shaft 10 passes through the wall of vessel 1 to rotor 4. Also passing through the wall of vessel 1 is a makeup feed line 11 coming from pump 12, which may be preceded by filter 13. That is, the makeup fluid to be treated may pass to filter 13 and then through line 15 to pump 12 for introduction to the boiler through feed line 11.

As explained above, rapid turning of the rotor 4 will cause cavitation within the fluid, thereby elevating the temperature of the fluid, ultimately to the boiling point. Pressure and temperature regulators not shown may, at the operator's discretion, establish boiling conditions other than atmospheric. Increasing the pressure within the vessel 1 above atmospheric may beneficially affect the cavitation process by enhancing the violence of the mini-implosions taking place in the cavities, but the viscosity of the fluid and the velocity of the outer surface of the rotor are also important factors which the operator should consider. Reducing the pressure below atmospheric (as by a vacuum pump for inducing subatmospheric pressure) may help increase throughput and reduce the energy requirements of the cavitation device. Other variables of interest are the number and depth of the cavities and the flow paths of the fluid in the particular construction of the boiler vessel. Our basic invention, however, heats the fluid directly, while immersed in the vessel, without flame or heat exchange surfaces, and boils water in it for direct delivery of steam or vapor. The vessel is able to contain and handle both the hot or boiling water 20 and, in a free space above the water, steam 21.

In FIG. 2, the cutaway view of vessel 1 reveals the uncovered and featureless circular face 7 of rotor 4 and illustrates the proximity of cavities 5 to the interior surface of housing 6. Circular face 7 need not be planar—to reduce drag or for any other reason, it could be recessed. An alternative incoming fluid feed line 16 enters the vessel 1 at port 17.

In FIG. 3, a variation is shown in which the motor 38 for the cavitation device is immersed in the vessel along with the cavitation device. The vessel 33 is represented as a typical tank used at a production site for fracturing fluid in hydrocarbon recovery, for example, a used fluid in need of a reduction in volume, or a fracturing fluid deemed too cold for use, and simply in need of heating. The cavitation device is shown in a horizontal mode—that is, on a vertical axis, unlike FIGS. 1 and 2; the cavitation device and the motor have been positioned in the tank through manhole 37. Supports 30 hold and steady the housing 31 which substantially surrounds the cylindrical surface of rotor 32 in a manner similar to the housing and rotor in FIGS. 1 and 2. Supports 30 do not impede the flow of fracturing, drilling, or other aqueous fluid from under rotor 32. Aqueous fracturing fluid already in the tank (vessel 33) flows through supports 30 and enters the interior of rotor 32. As explained with reference to FIGS. 4 a-d and FIG. 5, and elsewhere herein, centrifugal force in the rotating rotor 32 impels the fluid through radial channels (FIG. 5) to the substantially cylindrical surface of rotor 32, where it flows in the narrow space between rotor 32 and housing 31. In the narrow space between rotor 32 and housing 31, the fluid is subjected to the cavitation effect described elsewhere herein, and undergoes a significant increase in temperature, exiting above the rotor 32, where it circulates into the body of fluid 37 in the tank or vessel 33. So long as the rotor rotates, fluid continuously circulates and becomes elevated in temperature, ultimately, if desired, making steam or vapor which is contained in the upper region 35 of the vessel 33. A steam or vapor outlet or vent 36 is connected at the top of the vessel for use of the steam or vapor as needed or for release to the atmosphere. Where vessel 33 is not used for boiling but simply heating a fluid as may be the case with certain oilfield fluids otherwise ready for use, vent 36 may be used simply to let the tank “breathe.” Where the intent is to make steam, vent 36 may be assisted by vacuum, and accordingly the temperature of the steam or vapor may be lower than atmospheric boiling. Any suitable level control, not shown, may be used to balance the incoming fluid against the volume of steam or vapor released or taken for a useful purpose, together with any blowdown deemed necessary from a blowdown conduit not shown. The blowdown or concentrate may also be used, for example to recover and recycle chemicals used in an industrial process; for example to recycle densifying salts used in completion or workover fluids in the oil industry. Motor 38 and its electrical connections should, of course, be watertight and insulated for immersed use.

FIG. 3 illustrates that a cavitation device may be used simply to heat a fluid in a tank, and that the versatile cavitation device can be readily placed in a tank and removed as desired. It should be understood that the concept of immersing an entire cavitation device including its motor is applicable to the vessels described with respect to FIGS. 1 and 2—that is, motor 9 could be submerged in vessel 1, makeup liquid could be introduced either directly to the rotor of the cavitation device or simply though the vessel wall, provisions could be made for blowdown, and all other aspects of the invention are applicable whether the motor is within the vessel or outside of it.

FIG. 4 a is an outline perspective of a rotor useful in our invention, and FIG. 4 b is a lateral section of the rotor. They illustrate that the numerous cavities 40, similar to cavities 5 in FIG. 1, need not necessarily be aligned straight across the cylindrical surface of the rotor 41. The cavities 40 are bored or otherwise formed into the rotor 41. Also to be noted is that the face of the rotor 41 is not featureless as is face 7 in FIG. 2—rather, it is somewhat hollowed and includes several apertures 43 arrayed around the central receptacle 42 for a shaft from the motor (not shown). Apertures 43 may pass entirely through the thickness of the rotor, as depicted. Also, the opening 44 of a radial channel is seen in each aperture 43. As illustrated by dotted lines in FIG. 4 b, each radial channel 45 leads from an opening 44 in an aperture 43, in particular aperture 43 a, to an outlet 46 on the cylindrical surface of rotor 41.

In FIG. 4 c, Section A-A of FIG. 4 b is shown. Radial channel 45 begins at opening 44 and terminates at outlet 46, in the center of cylindrical surface 48 of the rotor 41. Aqueous fluid may enter opening 44 from either side of aperture 43 a to gain access to opening 44. Radial channels 45 need not be restricted to their central location within the rotor—that is, radial channels 45 may have outlets 46 nearer the edge of the cylindrical surface of rotor 41 rather than being centrally located. Persons designing such a rotor will probably wish to balance the number of channels on each side of the rotor. In the lower side of Section A-A, as depicted in FIG. 4 d, will be seen two cavities 40 a and 40 b. In this variation of the invention, the cavities comprise sections of relatively wide diameter 49 and sections of relatively narrow diameter 50. Unlike the radial channels 45, the cavities are “dead end,” and do not communicate with aperture 43 b. Such dead end cavities, having wider opening ends than closed ends, have been found to generate cavitation more efficiently than bores of constant diameter.

Each of the apertures 43 may have an opening 44 leading to a radial channel 45; thus in this variation, there are six such radial channels, as there are six apertures. We do not intend to be limited to six apertures or six radial channels. Any convenient number of each may be used, and it should be understood that the apertures, or some of them, need not pass completely through the rotor 41. And, while the channels should pass from an opening near the axis of the cylindrical rotor through the interior of the rotor to exits on its cylindrical surface, they need not be oriented as radii of a circular section of the rotor—that is, they may be oriented at an angle, as will be shown in FIG. 5.

FIG. 5 is a central plane section, orthogonal to the axis of its cylindrical shape, of one possible rotor 41, In this case, there are eight apertures 60 in view, each opening to a channel 61. Interior channels 61 are substantially true radials—that is, they follow the paths of true radii of the cylindrical section, except that they do not begin at the center of the rotor. Channels 62 are set at an angle θ from a true radius, as seen by the dotted lines and the symbol θ. Each of the channels 61 and 62 leads from an aperture 60 to the cylindrical surface of the rotor. A limited number of dead end cavities 64 are also illustrated, showing a wide top and a narrow extension. Many additional cavities and interior channels may be designed into the rotor. The wide opening and portion of the cavities near the cylindrical surface, and the narrower extension portions closer to the axis of the rotor, may be varied in design. The angle θ may vary considerably, from zero degrees to 60 or more degrees; angled channels 62 need not be of the same angle. Shaft 65 is ready for turning by a motor. The reader is reminded that FIG. 5 represents a slice through the rotor, and that, depending on the particular design, at least two other levels of channels and cavitities could be seen (see FIG. 4 a, for example). Indeed, the rotor can be constructed to have numerous channel exits and cavities spread across the cylindrical surface 48 of the rotor.

In FIG. 6, the vessel 70 has an internal diameter slightly larger than the diameter of rotor 71, so that the cylindrical wall of vessel 70 can act as the cylindrical housing in the constructions shown in FIGS. 1 and 2. Rotor 71 is rotated by motor 72 through shaft 73. Rotor 71 is of a construction similar to that of FIGS. 4 a-4 d and 5, and accordingly the incoming fluid from line 74 enters apertures not shown on the lower surface of rotor 71, is thrust by centrifugal force through radial and/or somewhat angled channels to the outlets 75 on rotor 71. As in FIGS. 4 a-4 d, rotor 71 has a plurality of cavities 76 which cause cavitation of the fluid in the narrow space 77 between the rotor 71 and the wall of vessel 70, thus heating the fluid. From the space 77, the fluid may flow either downwards and back into the apertures for recirculation and further heating, or upwards into the boiling water holding space 78. Steam forming in the top of vessel 70 can be removed initermittently or continuously through line 80. Blowdown or hot liquid removal may be performed through line 79, and the boiling and steam generation process may be modulated by any convenient level control or other control devices, using flow readings from the incoming fluid, the blowdown, and the steam output, as well as conventional level viewer 81. All of the variations of the invention shown herein may also utilize pressure, temperature and other meter or transducer signals together with the flow readings, level, valves, pumps, controllers and the like to regulate inputs and outputs of the boiler vessel as desired. The vessel 70 need not be shaped as shown, as substantially cylindrical, but could have wider or narrower dimensions above or below the rotor 71, or both. FIG. 6 is intended to illustrate that the wall of the vessel 70, or a portion of it, can serve the function of the substantially cylindrical housing 6 of FIG. 1 or 2, 31 of FIG. 3, 85 of FIG. 7, or 22 of the water brake of FIG. 8, although for the last purpose, additional provision should be made for circulation of the aqueous fluid from below the water brake to above it, and from above to below if desired.

In FIG. 7, the housing 85 for the cavitation device is seen to have a vertical extension 86. Here also the rotor 87 is mounted on a vertical axis, shaft 88 emanating from electric motor 89. Incoming fluid in line 93 may be filtered in optional filter 94 and pumped by pump 95 either to a featureless face on the rotor 87 as in FIG. 2, or a face similar to that shown in FIGS. 4 a-4 d, or anywhere into the boiler vessel, as through the side of vessel 90. If the fluid is directed to the face of the rotor similar to that of FIG. 2, the fluid is diverted directly to the side of vessel 90, as indicated by the lower arrows 97. If it has apertures and channels as illustrated in FIGS. 4 a-4 d, the fluid will be directed through the rotor 87 and be thrust by centrifugal force out of the channels (not shown) to outlets 91, where it will immediately encounter housing 85. The fast-rotating rotor 87 will cause shearing and tortuous flow between the surfaces of the rotor and housing 85; when the fluid passes over one of the cavities 92, it will attempt to fill the cavity, but will immediately be ejected by centrifugal force, as previously explained, thus creating a semi-vacuum, which is immediately imploded. The violence of such cavitation converts the mechanical energy of the rotor into thermal energy within the fluid, quickly elevating its temperature. In either mode—that is, whether or not the fluid is able to pass through one or more channels in the rotor, the fluid in vessel 90 substantially constantly circulates by entering the top of vertical extension 86, as indicated by upper arrows 98. The fluid flows downwardly in extension 86, then to the extremities of the rotor 87 within housing 85, where it is again subjected to the heating action of cavitation. If salts and/or solids accumulate in the heated fluid, a blowdown may be conducted as desired through blowdown line 96. In some instances, the blowdown concentrate will contain valuable constituents which may be recovered in a known manner for recycling or other uses. Motor 72 in FIG. 6 and motor 89 in FIG. 7 could alternatively be located within the boiler vessel, as illustrated by the embodiment of FIG. 3.

FIG. 8 is a section of a vessel 1 containing a water brake, sometimes known as a dynamometer or a water brake dynamometer. Such a device is within our definition of a flux stress device, as indicated above. In FIG. 8, the depiction of the water brake is modified from an illustration in Wikipedia. The water brake comprises a rotor 23 within a stator 22 desirably fixed within the vessel 1 by supports or struts not shown. Rotor 23 is fixed to a shaft 10 which is rotated by a motor not shown, outside the vessel, although, as explained elsewhere herein, a submersible motor may be used within the vessel. Annular cavities 24 and 25 are defined by the stator 22 and rotor 23. Annular cavity 24 is filled with aqueous fluid entering from outside the vessel through conduit 26. Annular cavity 25 is filled with aqueous fluid 20 from inside the vessel 1, entering through port 28. Either or both annular cavities may be filled with aqueous fluid either from outside the vessel or from inside the vessel; if both obtain fluid from inside as through port 28, a feed line such as feed line 16 in FIG. 2 may be used to place makeup fluid in the vessel 1 either continuously or intermittently; such a source of fluid is recommended in any event. Rotor 23 is caused to rotate on shaft 10 within the stationary stator 22, causing considerable turbulence within the annular cavities 24 and 25, and also causing the fluid to be ejected from the annular cavities by centrifugal force, through cavity exits 27 near the outer edges of the cavities. Aqueous fluid thus circulates from the entrance points near the axis of rotation of the rotor (conduit 26 and port 28) to cavity exits 27 near the outer edge of the rotating rotor, becoming heated from the agitation and turbulence caused by its position between the rotating rotor 23 and the motionless stator 22. The more or less constant flow of fluid into and out of the water brake and the differing temperatures of the entering and exiting streams of fluid cause a constant circulation of fluid within the vessel 1, which provides a means for control of the temperature in the vessel. A level tube 81 may be used to monitor level, and various thermocouples transducers, valves, flow meters, pressure monitors and controls, and other devices not shown may be used to achieve the desired temperatures and pressures, including pressures lower than atmospheric in the free zone 21 above the fluid 20 if so desired. Steam or vapor may be removed through outlet line 3 and blowdown conducted through blowdown line 2.

Therefore, it is seen that our invention comprises a reservoir including a flux stress device, which may be a cavitation device, within the reservoir, which may be a boiler vessel. The cavitation device may comprise a rotor for immersion in liquid, the rotor comprising a body having a substantially cylindrical surface and two faces, the body having a central opening on at least one face for receiving a rotatable shaft for rotating the rotor and a plurality of channels for admitting liquid when the rotor is immersed in the liquid and transporting it to the substantially cylindrical surface, and a plurality of cavities on the substantially cylindrical surface. A submersible electric motor may be used, to place the entire flux stress device, including the motor, in the reservoir. In a particular variation, our invention is a boiler apparatus comprising a substantially cylindrical vessel having a substantially cylindrical interior surface, and a substantially cylindrical cavitation rotor within the vessel, the substantially cylindrical rotor also having a substantially cylindrical surface, the cylindrical rotor surface having a diameter slightly smaller than the interior surface of the substantially cylindrical vessel, the rotor surface and the interior surface being substantially concentric. And, our invention includes a method of substantially continuously or intermittently heating an aqueous fluid comprising placing the aqueous fluid in a reservoir such as a boiler vessel and causing cavitation or other flux stress within the aqueous fluid in the reservoir, which may be substantially continuously or intermittently replenished. The reservoir may be a tank and the aqueous fluid may be an oilfield fluid such as a fracturing fluid. 

1. Apparatus for heating a liquid comprising a reservoir, a flux stress device within said reservoir capable of heating liquid in said reservoir by flux stress when said flux stress device is immersed in said liquid, an inlet for admitting makeup liquid to said reservoir, and at least one outlet from said reservoir for removing liquid heated by said flux stress device, said liquid being removed as heated liquid, vapor or steam.
 2. Apparatus of claim 1 wherein said flux stress device includes a rotor which generates flux stress in a liquid when it is immersed in said liquid and rotated.
 3. Apparatus of claim 2 including a motor or engine for rotating said rotor, said motor or engine being located within said reservoir.
 4. Apparatus of claim 2 including a motor or engine for rotating said rotor, said motor or engine being located outside said reservoir.
 5. Apparatus of claim 1 including a conduit for makeup liquid leading to said inlet.
 6. Apparatus of claim 5 including a filter in said conduit.
 7. Apparatus of claim 1 wherein said reservoir is a boiler vessel capable of containing up to 250 pounds per square inch pressure.
 8. Apparatus of claim 7 wherein said boiler vessel is capable of containing at least 500 pounds per square inch pressure.
 9. Apparatus of claim 1 wherein said flux stress device is a water brake dynamometer.
 10. Apparatus of claim 1 wherein said flux stress device is a cavitation device.
 11. A liquid reservoir including a cavitation device within said liquid reservoir.
 12. The liquid reservoir of claim 11 wherein said cavitation device comprises a rotor having cavities for inducing cavitation in a flowing liquid, and a housing defining a path for said flowing liquid, said path passing by said cavities.
 13. The liquid reservoir of claim 12 including an aqueous fluid in said reservoir in an amount sufficient to submerge said cavitation device.
 14. The liquid reservoir of claim 13 including means for substantially continuously introducing makeup liquid to said liquid reservoir and substantially continuously removing at least one of heated liquid, steam, or vapor from said reservoir.
 15. A boiler vessel including a cavitation device within said boiler vessel.
 16. The boiler vessel of claim 15 wherein said cavitation device comprises a rotor having cavities for inducing cavitation in a flowing liquid, and a housing defining a path for said flowing liquid, said path passing by said cavities.
 17. The boiler vessel of claim 15 including an aqueous fluid in amount sufficient to submerge said cavitation device.
 18. The boiler vessel of claim 15 including an outlet for steam and vapor.
 19. The boiler vessel of claim 15 including an outlet for blowdown.
 20. The boiler vessel of claim 15 including a conduit for introducing incoming aqueous fluid to said boiler vessel.
 21. The boiler vessel of claim 15 including means for inducing subatmospheric pressure within said vessel.
 22. The boiler vessel of claim 20 including a filter on said conduit for introducing incoming aqueous fluid.
 23. The boiler vessel of claim 20 wherein said conduit for introducing incoming aqueous fluid to said boiler vessel introduces said aqueous fluid through said cavitation device.
 24. The boiler vessel of claim 23 including a filter on said conduit for introducing incoming aqueous fluid.
 25. The boiler vessel of claim 16 wherein said rotor is mounted on a substantially horizontal axis.
 26. The boiler vessel of claim 16 wherein said rotor is mounted on a substantially vertical axis.
 27. The boiler vessel of claim 15 wherein said boiler comprises a substantially cylindrical vessel and said cavitation device comprises a substantially cylindrical rotor having cavities on its surface, said cavities being disposed in proximity to the interior wall of said substantially cylindrical vessel.
 28. The boiler vessel of claim 15 wherein said cavitation device includes a submersible motor for powering said cavitation device, which motor is also within said boiler vessel.
 29. A cavitation device rotor for immersion in liquid, said rotor comprising a body having a substantially cylindrical surface and two faces, said body having a central opening on at least one face for receiving a rotatable shaft for rotating said rotor and a plurality of channels opening on at least one face for admitting liquid when said rotor is immersed in said liquid and transporting it to said substantially cylindrical surface, and a plurality of cavities on said substantially cylindrical surface.
 30. The cavitation device rotor of claim 29 wherein said cavities are wider at their outlets than in their portions closer to the axis of said rotor.
 31. The cavitation device rotor of claim 29 wherein said channels are substantially radial channels.
 32. A cavitation device for immersion in a boiler vessel comprising the rotor of claim 29 and a housing substantially surrounding and in proximity to said substantially cylindrical surface of said rotor.
 33. The cavitation device of claim 32 including a submersible electric motor for turning said rotor.
 34. Boiler apparatus comprising a vessel, a cavitation device rotor of claim 29 in said vessel, and a housing substantially surrounding and in proximity to the substantially cylindrical surface of said rotor.
 35. Boiler apparatus comprising a vessel having a substantially cylindrical interior surface in at least a portion of said vessel, and a substantially cylindrical cavitation rotor within said vessel, said substantially cylindrical rotor also having a substantially cylindrical surface, said cylindrical rotor surface having a diameter slightly smaller than at least a portion of the interior surface of said vessel, said rotor surface and said portion of said interior surface being substantially concentric.
 36. Boiler apparatus of claim 35 wherein said cavitation rotor has a plurality of cavities on said substantially cylindrical surface and a plurality of interior channels for transporting liquid from near the center of said rotor to said substantially cylindrical surface thereof.
 37. Boiler apparatus of claim 35 including a submersible motor within said vessel for powering said cavitation rotor.
 38. Method of heating an aqueous fluid comprising placing said aqueous fluid in a boiler vessel and causing cavitation within said aqueous fluid in said boiler vessel.
 39. Method of claim 38 including continuously or intermittently feeding said aqueous fluid to said boiler vessel.
 40. Method of claim 38 including continuously or intermittently removing steam or vapor from said boiler vessel.
 41. Method of claim 38 including continuously or intermittently removing blowdown or hot aqueous fluid from said boiler vessel.
 42. Method of claim 38 wherein said cavitation is accomplished by a cavitation device.
 43. Method of providing hot aqueous liquid or steam comprising substantially continuously passing aqueous liquid into a reservoir, inducing flux stress in said liquid while it is in said reservoir, thereby elevating the temperature of said liquid, and substantially continuously removing said liquid from said reservoir in a liquid or gaseous state.
 44. Method of claim 43 wherein said flux stress is induced primarily by shear.
 45. Method of claim 43 wherein said flux stress is induced primarily by turbulence.
 46. Method of claim 43 wherein said flux stress is induced primarily by cavitation.
 47. Method of heating an oilfield fracturing fluid in a tank comprising immersing a cavitation device in said tank and operating said cavitation device to induce cavitation in said fracturing fluid, thereby elevating its temperature.
 48. Method of claim 47 wherein said cavitation device includes a submersible motor.
 49. Method of removing water from a dilute oilfield fluid comprising heating said dilute oilfield fluid in a boiler vessel of claim 15 and removing steam or vapor therefrom.
 50. Method of claim 49 including drawing a vacuum on said boiler vessel. 